The present invention relates to a method of manufacturing a semiconductor light emitting device, which forms a semiconductor layer laminate including a p-type layer and an n-type layer on a wafer-like substrate and then breaking down the wafer into individual chips. More particularly, this invention relates to a method of manufacturing a semiconductor light emitting device that can facilitate breakdown of such a wafer whose substrate is hard to break into individual chips as in the case of a semiconductor light emitting device for bluish color which has a gallium nitride-based compound semiconductor layer laminate formed on a sapphire substrate.
A conventional method of fabricating chips of semiconductor light emitting devices (hereinafter called LED chips) which emits bluish light is carried out as follows. As shown in FIG. 3, an n-type layer (clad layer) 23 of, for example, n-type GaN, an active layer (light emitting layer) 24 of a material whose light emitting wavelength is so determined as to provide a smaller band-gap energy than that of the clad layer, e.g., an InGaN-based (which means, throughout the specification, that the ratio of In to Ga is variable) compound semiconductor, and a p-type layer (clad layer) 25 of p-type GaN are epitaxially grown in order on a sapphire substrate 21. P-side (upper) electrodes 28 are provided on the top surface of the p-type layer 25, and n-side (lower) electrodes 29 are provided on the top surface portions of the n-type layer 23 which have been exposed by locally etching the semiconductor layer laminate. Then, the resultant structure is scribed at boundary portions S between chips with a diamond scriber or the like, forming notches 21a. Force is applied to the notch portions 21a to break the structure into individual chips. With regard to the n-type layer 23 and the p-type layer 25, an AlGaN-based (which means, throughout the specification, that the ratio of Al to Ga is variable) compound semiconductor layer is frequently used by the side of the active layer 23 in order to enhance the carrier trapping effect. Further, at the time of etching the aforementioned semiconductor layer laminate, those portions at the boundary portions S between the chips at which breaking will take place are simultaneously etched to expose the n-type layer 23, thus facilitating the breakdown process.
To break a wafer into individual chips, as apparent from the above, the conventional fabrication method employs a scheme of locally etching the semiconductor layer laminate to make it thinner and forming notches at the back of the substrate before chip separation. If a rigid substrate like a sapphire substrate is used, however, notches are merely formed shallow which makes it very difficult to break the rigid sapphire substrate at the notches. What is more, although the semiconductor layer laminate is locally etched on the top surface side of the substrate, part of the semiconductor layer laminate like the n-type layer, which is of a different material from that of the substrate, still remains attached to the substrate. This makes it harder to break the substrate. Even if the substrate is forcibly broken down to chips, therefore, cracking is likely to occur at the non-etched side of the semiconductor layer laminate, damaging the light emitting layer portion like the active layer.